Acknowledgment
Communiqué IIT Kharagpur recognises the contribution of
its Executive Team 2019-2020 as the main authors from the
book, however various sections of interview experiences on
Quora.com and Glassdoor.com have been reproduced. Parts
of casebooks by IIMA, ISB, and LSB, also The Guesstimate
Compendium have been referred to and included in the book.
All rights of the book are reserved. The authors have the
right to come up with new versions, add/subtract content,
and credits. No part of this book may be stored electronically
or mechanically, photocopied or stored as a video unless
specified by the authors. Any infringements will be strictly
dealt with.
1|The Guessing Game
I​NDEX
PAGE NO.
CASE
1-3
Estimation of the number of petrol pumps in Delhi.
4-6
Estimate the amount of revenue generated by a single petrol
pump.
7-8
Estimate the length of road in Delhi:
9
Estimate the number of planes at the Delhi Airport.
10-11
Estimate the number of planes starting or terminating to Delhi
in a day.
12-13
Estimate the number of planes flying over India at this very
moment.
14
Estimate the number of traffic lights in Delhi.
15-17
Estimate the number of CCTV Cameras in Mumbai.
2|The Guessing Game
18-19
Estimate the number of schools in Delhi.
20-21
Estimate the number of hospitals in Delhi
22-23
Estimate the number of ATMs in Delhi
24
Estimate the number of Band-Aids sold in India
25-26
Estimate the number of people traveling in Metro (Delhi Metro).
27-28
Estimate the number of copies of Sherlock Holmes sold in India
this year.
29-30
Estimate the number of gulab jamuns sold in Delhi on a single
day.
31-32
Estimate the number of cars crossing Delhi-Gurgaon toll in a
day
33-35
Estimate the revenue of an MCD outlet coming out from a
burger sales
36-40
Estimate the number of televisions and refrigerators sold in
Delhi in a year (Also estimate the revenue) :
3|The Guessing Game
41- 42
Number of iPhones sold in India
43-44
Number of paracetamol tablets sold in Delhi
45-46
Estimate the number of lakes in the world:
47-48
Estimating the size of the tyre industry in India in 2020
49-50
The number of roses sold in Delhi on 14​th​ February
51-52
The number of footballs sold in India:
53-54
Number of students attending 10th/12th/college in India
55
The number of golf balls that can fit in the room
56
Estimate the number of hair on your scalp
57-58
Estimate the number of people traveling in Metro (Delhi Metro)
59-60
Estimate the number of copies of Sherlock Holmes sold in India,
this year
61-62
Estimate the number of gulab jamuns sold in Delhi on a single
day
63-64
Estimate the number of cars crossing Delhi-Gurgaon toll in a
day
65-67
Estimate the revenue of an MCD outlet coming out from a
burger sales
4|The Guessing Game
68-70
Estimate the number of televisions and refrigerators sold in
Delhi in a year (Also estimate the revenue)
71-72
Number of iPhones sold in India
73-74
Number of paracetamol tablets sold in Delhi
75-77
Estimate the no. of lakes in the world
78-79
Number of roses sold in Delhi on 14​th​ February
80
Estimate the average distance run by a football player in an
average match. (45-90 meters and 90-120 meters)
81-82
Estimate the power consumed in your house in a day
83-84
Estimate the number of youtube videos streamed in Delhi on a
day
85-86
Estimate the number of SRK fans in India.
5|The Guessing Game
87-88
Estimate the amount of money drawn from an ATM machine in
Delhi in one day
89-90
Estimate the market size of formal ties in India on an annual
basis.
91-92
Estimate the annual size of socks sales in India.
93-94
Estimate the daily amount of water consumed by an Indian.
95-97
Estimate the number of Indians on Twitter.
6|The Guessing Game
7|The Guessing Game
CASE -1
Estimation of the number of petrol pumps in Delhi.
Approach 1:
Petrol pumps are located on the sides of roads, generally major roads and highways. So,
we will estimate the length of all the major roads and highways and then place two petrol
pumps at a suitable distance.
Area of Delhi:
Assume Delhi to be a square with Metro's blue and yellow line being as shown in the
figure.
We assume that there are 30 metro stations each on both the routes and average distance
between two stations being 2km.
Therefore, approximate area of Delhi= 0.5x60x60 = 1800sqkm
Delhi region:
●
Residential use: 30% area
●
Commercial use: 25% area
●
Forest+ Agriculture use: 10% area
●
Roads network: 20% area
●
Others: 15% area
Area of roads in Delhi = 20% of 1800sqkm = 360sqkm = ~350sqkm
Roads types:
●
Municipal roads: 35%
=(~125)sqkm
●
State roads: 50%
=(~175)sqkm
●
Central good roads: 15% =(~50)sqkm
​State roads: (~175)sqm
● Main roads: ~50sqkm (30%)
: Approximate width of the road is 15m.
● Flyovers and Highways: ~35sqkm (20%)
: Approximate width of the road is 20m.
● Other interconnecting roads:~85sqkm(50%)
: Approximate width of the road is 10m.
1|The Guessing Game
Central good roads:(~50)sqm
4. Generally, highways and flyovers would have petrol pumps on almost every road:
Approximate width of the road is 25m.
Length of road of interest:
1. 50/0.015 =~3000km
2. 35/0.020 = 1750km
3. 85/0.010 = 8500km
4. 50/0.025 = 2000km
Total length would be approximately = 1500km
The average distance between 2 petrol pumps is generally 1-2 km, say 1.5 km.
Therefore, number of petrol pumps in Delhi
= 1500/1.5
= ​10000 pumps(approximately)
Note​: If the average distance is taken as 1km, then there would have been 15000 pumps,
and if the average distance would have been 2km, then there would have been 7500
pumps. Either number is good.
But if the interviewer said that 10k is a big number, then by taking the average distance
of 2km we can scale it down, and if it is a smaller number then by taking the average
distance as 1km, we can scale up the number.
Approach 2:
Delhi:
● 7 parliamentary seats (Central government)
● 70 legislative seats (State government)
● 235 wards (municipal council)
Delhi:
● Forest/Agriculture area = 10%
● Residential area = 30%
● Commercial (offices) = 30%
● Infrastructure and other miscellaneous areas(like parks,etc.) = 20%
● Industries = 10%
The approximate number of petrol pumps in residential and commercial areas = 50 per
ward
2|The Guessing Game
The approximate number of petrol pumps in Forest/Agriculture areas = 30/ward
(More number of diesel pumps will be present than petrol pumps as tractors, trucks
require diesel and not petrol.)
The approximate number of petrol pumps in miscellaneous areas and industries =
20/ward
Calculation:
● Residential and commercial areas:
= (30+30)×50×235/100
= 30×235
= 7050 pumps
● Agriculture/Forest areas:
= 10×30×235/100
= 705 pumps
● Miscellaneous areas and industries:
= 30×20×235/100
=​ 1410 pumps
Approximately, the total number of pumps = ​9165 pumps.
Note again if we are asked to scale up or down a number we can do so by increasing or
decreasing the number of petrol pumps per ward in different regions. How did we get to
this number, of say, 50 pumps per ward in a commercial area?
We can defend this by saying that we have estimated this based on what we saw during
our visit to Connaught Place.
Note: S
​ plitting the region into constituencies, legislative assembly seats or municipal
wards can be a beneficial technique.
3|The Guessing Game
CASE -2
Estimate the amount of revenue generated by a single petrol pump.
Note:​ Here, revenue generated implies money generated. If the question was framed as
the sales generated by a petrol pump, then there we should ask a clarifying question as to
what they mean by sales- revenue( money generated by sales) or the amount of petrol
sold(in litres).
Also, a good clarifying question can be to be sure that we need to consider the petrol pump
to sell only petrol or do we need to consider diesel and gas sales as well.
Let us consider that the petrol pump sells petrol and diesel.
Petrol pump:
● Four petrol stations
● Two diesel stations
Petrol type:
● Normal (regular)
● Power (extra refined)
We will assume that a petrol pump is operational for 20 hours, starting from 6 am till 2
am : (6 am-12 am) and (12 am-2 am)
Also, we will assume that the average time taken to serve a customer is ninety seconds or
forty customers can be served by a station in one hour.
However, the petrol pump never runs at full efficiency.
Assuming a working day: 6 A.M. - 2 A.M.
● 6A.M. - 11 A.M.
School and office traffic
Occupancy @ 80%
● 11A.M. - 2P.M.
Relatively low traffic
Occupancy @ 50%
● 2P.M. - 7P.M.
School and office traffic
Occupancy @ 80%
4|The Guessing Game
● 7P.M. - 11P.M.
Relatively thin traffic
Occupancy @ 60%
People going out for dinner, movies and those returning from a job.
● 11P.M. - 2A.M.
Selective people are out of their home.
Occupancy @ 30%
Note: I​ f there would have been a weekend then the traffic in the morning will be low.
That will be compensated in the afternoon and evening when people move out to travel.
Also, Generally, people purchase in fixed denominations such as {50, 100, 200}
(Two-wheelers generally), {500, 1000, 2000} (Cars and trucks generally).
Approach :
First, we will calculate the number of distinct transactions made and then we will repeat
on the transaction site.
# of transaction = # of hours​ x ​occupancy​ x​ maximum feed rate​ x​ # of station
=( 5X0.8X40X6) + (3X0.5X40X6) + (5X0.8X40X6) +
(4X0.6X40X6)+ (3X0.4X40X6)
= 40 X 6 X ( 4 +1.5 + 4 + 2.4 + 1.2)
= 40 X 6 X 12.7
= 76.2 X 40 = 3048 transactions per day
~ 3000 transactions per day
Out of these 2000 were petrol-based and 1000 were diesel-based ( as there were four
petrol stations and two diesel station. )
We assume that diesel transaction = {500 (for 33% time) , 1000 (for 33% time) , 2000
(for 33% time)}
Therefore, Weighted average ~ 1200
Revenue generated from diesel station = 1200 X 1000
= 1200000
= 1200K or 12 Lakh
Petrol:
● 70% two wheelers approx 100/ “/?”
● 30% of Cars
1. Regular
⅔ of the total approximately 750/ “/?”
5|The Guessing Game
​Power:
​⅓ of the total approximately 750/ “/?”
4 X 2000 X 0.7 X 100 + 4 X 2000 X 0.3 X 750
=560K + 1800K
Total revenue from Petrol station = 2360K
Total Revenue = 2360K + 1200K = 3560K (or 35.6 Lakh Revenue)
Additional Help:
Amount of diesel sold
= 1200K (Average price of diesel)
Diesel cost say 50 per Litre
= 1200/50 K Litres = 24000 L
Amount of petrol sold (in Litres) = [1200/70]K (Regular) + [600/75]K (Power)
= 17000 L + 8000 L
Therefore, Total of​ 25000 L​.
Note: R
​ emember to defecate as much as possible.
Notice that diesel is used by heavy-duty vehicles such as buses, SUVs etc. So, they will be
refuelling in larger quantities than bikes and other two-wheelers.
Also, note that the # of two-wheelers is much higher than the # of four-wheelers. Hence,
the spend on these two categories being different affects the revenue generated.
Also, notice that we have considered the money spent on each transaction. In India
generally, we refuel based on a fixed denomination. We don’t go out to refuel with the
mindset that we need to purchase 10 L of fuel, for the car and so on.
6|The Guessing Game
CASE -3
Estimate the length of road in Delhi:
Approach :
We will begin by estimating the total area, which gives the area of roads, which further
gives the length of the road.
Assume Delhi to be a square and Yellow and Blue metro lines run diagonally to each
other. Each has 30 stations situated in Delhi with an average distance between them to be
2KM.
`
Therefore, Area of Delhi = ½ X (Diagonal)^2 = ½ X (2 X 30)^2 = 1800 sq.km
Delhi Area:
● Residential (30%)
● Commercial (20%)
● Forest / Agriculture (10%)
● Roads (20%)
● Others such as park, temples, malls, industries (20%)
Therefore, Area of Delhi Roads = 20% of 1800 sq km
= 360 sq. km
Types of Roads:
● Maintained by MCD (50%)
These are small roads interconnecting roads, in-roads to society and other
residential or commercial areas.
● Maintained by State Government (30%)
These are larger main roads and highways.
● Maintained by the Central government (20%)
These are used to connect one state to another. These are national highways and
flyovers.
Calculations:
1. Approximate width of National highways and Flyovers = 25 Miles ( They are
broader as they are multi-lane highways and expressways.)
Therefore, Length of road = ((0.2 X 360)/25) X 1000
7|The Guessing Game
= 8 X 360 = 2880KM
2. The approximate average width of State-owned roads = 15 Meters (These are
generally smaller in width than National Highways.)
Therefore, Length of road = (0.3 X 360 X 1000)/15 = 7200KM
3. Approximate width of roads maintained by MCD = 10 Meters (These are
generally smaller feeder roads and in-roads to societies.)
Therefore, Length of road = (0.5 X 360 X 1000)/10 = 18000KM
Total Length = 2880 + 7200 + 18000 KM
=​ 28080 KM
8|The Guessing Game
CASE -4
Estimate the number of planes at the Delhi Airport.
Note that here, we have to guess the number of planes currently standing at the airport,
i.e. at this moment.
Approach :
Delhi Airport:
● Terminal 1: This has, say 3 runways.
● Terminal 2: This has, say 3 runways.
● Terminal 3: This has, say 6 runways
.
Calculations:
Since it is broad-daylight, the airport is expected to run at near full operational capability.
Let us assume that the time to take off / land a plane is 2 minutes. Further, the time to
board or deboard the plane is 1 hour.
This means, currently we can estimate:
= (12 runways) x (1 hr)/(2 min)
= 12 x 30 = 360 planes.
Additionally, we can assume a certain percentage of planes (say an additional 10%) which
may be running late or are parked due to technical issue glitches.
Therefore, total numbers of planes = 360 + 0.1 x 360 = ​396 planes​.
9|The Guessing Game
CASE -5
Estimate the number of planes starting or terminating to Delhi in a day.
Delhi Airport:
● Terminal 1: This has, say 3 runways.
● Terminal 2: This has, say 3 runways.
● Terminal 3: This has, say 6 runways.
Since it is broad-daylight, the airport is expected to run at near full operational capability.
Let us assume that the time to take off / land a plane is 2 minutes.
Further, approximately 30 planes can land on a runway in one hole.
Percentage efficiency of airport
11 pm to 6 am
6 am to 12 pm
12 pm to 5 pm
5 pm to 11 pm
70%
90%
100%
100%
Note: H
​ ere, the fact that Delhi airport is highly crowded has been taken into account. So a
relatively low number of flights will include descent to good occupancy.
= 7 x 0.7 x 30 x 12 + 0.9 x 6 x 30 x 12 + 11 x 30 x 12
= 30 x 12 x (4.9 + 5.4 + 11)
= 30 x 12 x 21.3
= 639 x 12 = 7668 flights
So around 7500 / 8000 flights
Additional Question:​ E
​ stimate the number of people flying in and flying out from Delhi
in a day.
Types of bookings :
● Economy Class
10|The Guessing Game
● Economy Plus
● Business Class
= 7 column x 20 rows + 4 column x 15 row + (approx) 25 passengers
= Total 225 passengers (max capacity)
Let the arrange occupancy be 80% which implies, 180 passengers
People flying daily = 180 x 7500= 1,350,000
Note:​ ​These approx. Half of those who flew into Delhi and half of those who flew out of
Delhi.
Additional follow-up question: Estimate the revenue generated by all of these flight
tickets sales.
Types of booking are:
● Economy Class (60%): Average ticket price = 5000
● Economy Plus (30%): Average ticket price = 12000
● Business Class (10%): Average ticket price = 25000
Weighted average = 3000 + 3600 + 2500 = 9100 or 9000 approx
Revenue: 1.35 x 9000 million = 1
​ 3.15 billion
11|The Guessing Game
CASE -6
Estimate the number of planes flying over India at this very moment.
Number of Planes flying over India includes:
● All domestic and international flights, originating or terminating in India.
● Other International flights, flying over Indian airspace.
Part 1:​ ​All domestic and international flights, originating or terminating in India.
1. Tier-1 city = 20 cities (all of them have airports with many terminals and
runways)
2. Tier-1 city = 60 cities (80% of them have airports with single terminal and 3
runways)
3. Tier-1 city = 120 cities (20% of them have airports with single terminal and 2
runways)
Available runways = 20 x 1 x 2 x 3 + 80 x 0.6 x 1 x 3 + 120 x 0.2 x 1 x 2
= approx 300 runways.
Let's say that the runway operates at 75% efficiency.
= 0.75 x 300 = 225 runways.
Average time to take off is 2 minutes. Further to incorporate planes currently flying, we
take an average flight duration of 90 minutes.
Per runway approx 45 planes may be in Indian airspace. I.e. 225 x 45
= 900 + 112 = 1012 flights approx.
Part 2:​ ​Other International flights, flying over Indian airspace.
Approx 200 countries.
Europe to Oceania, Europe to Australia and New Zealand, and Africa to Oceania. Also,
we assume that each country in Europe travels to each country in Oceania with at least a
12|The Guessing Game
flight in 30 minutes which is approximately the time the plane may be lying over India.
Europe to Oceania and vice versa = 30 x 20 x 2 = 1200
Europe to Australia and New Zealand & vice versa = 30 x 2 x 2 = 120
Africa to Oceania and vice versa = 40 x 20 x 2 x 0.5 (not all countries in Africa have an
airports = 800
Total international planes = 120 + 1200 + 800 = 2120 planes
Total planes = 1012 + 2120 =​ 3132 planes
​ ote​: Here private planes are not being considered and government officials planes are
N
not being considered.
13|The Guessing Game
CASE -7
Estimate the number of traffic lights in Delhi.
ApproachEstimate the road and then estimate the traffic lights.
Area of Delhi=½(60)(60)sq. Km=1800 sq km
Residential-25%
Commercial-25%
Forest/agri-10%
Industry and other miscellaneous parts-20%
Roads-20%
Area of roadways=20% of 1800 sq km=360 sq km
Types of roads● Maintained by Municipal Corporation -35%=125 sq km
● Maintained by State Government(main roads, flyovers)-50%=175 sq km
● Maintained by Central Government-15%=50 sq km
A.​ Main roads(30%)-Almost 100% roads have a traffic light at an approximate distance
of 2 km
50 sq km
Width of road=15 m
B.​ Flyovers and highways(20%)-Almost all flyovers have a traffic light at an approximate
distance of 4km
35 sq km
Width of road=20 m
C.​ Other inter-connecting roads (50%)-Around 30% of them have a traffic light at an
approximate distance of 2 km
85 sq km
Width of road=10 m
Central Roads(50 sq km)D​. All of them have traffic lights at a distance of 8 km
Width of road=25 m
A--(50 X 1000)/(15 X 2)=1666
B--(35 X 1000)/(20 X 4)=4375
C--(85 X 1000 X 0.3)/(10 X 2)=12750
D--(50 X 1000)/(8 X 25)=250 Thus, ​19035 traffic lights.
14|The Guessing Game
CASE -8
Estimate the number of CCTV Cameras in Mumbai.
Approach
Where are CCTV Cameras used?
● They are used for safety and surveillance
● Banks
● Markets
● Hospitals
● Houses
● Malls
● Shops
● Office
● Colleges
The population of Mumbai=approx 21 million (or 2 crores)
Age-wise segregation of population● Infants (upto 3 years) --3% --(0.63 million)
● School-going age (4-18 years) --30% -- (6.3 million)
● 18-30 years -- 33% -- (7 million)-○ Can go to college-- 25% -■ 80% went to college
■ 20% did not go to college
○ Rest go to job
● 30-50 years -- 16.66% -- (3.5 million)
● 50 and above -- 16.66% --(3.5 million)
Assuming we have a bank branch for every 10,000 persons-Assuming 80% of people have an account in a bank
No. of bank branches=(14000/10000) X 1000 X 0.8 = 1120 bank branches
Let each branch has approximately 15 cameras
=1120 X 15 = 16800 cameras
Assuming we have a hospital for every 15000 persons-(21 X 1000 X 1000)/(15 X 1000)= 1400 hospitals
Each hospital has around 50 cameras
15|The Guessing Game
1400 X 50 =70000 cameras
Assuming we have a school for every 8 X 50 X 14 = 5600 =6000 approx students-1050 schools
Each school has approx 40 cameras-1050 X 40 = 42000 cameras
Assuming we have a college for every 2000 students
(7 X 1000 X 1000)/2000 X (¼) X (4/5) = 700 colleges
Let each college has 50 CCTV
50 X 700 =35000 cameras
Working people​-- 60% --(12.6 million)-● 6.3 million males (All working)
● 6.3 million females (⅓ working)--2.1 million
Total working people​ = (6.3 +2.1)million=8.4 million-● Office ( 75%)--6.3 million
● Shops (25%)--2.1 million
An office per 500 people on an average, 100 cameras per office
6300 X 1000 X 100/500=1.26 lac cameras
A shop for every 10 persons, 10 cameras per shop
21000 X 1000 X 10/10=2.1 million
Population=21 million
Average family size in India is 4-5.
-> 4 to 5 million families= 4.5 million families-● Below poverty line ( 10%) --None will have cameras installed
● Low middle class (40%) -- 30% will have cameras installed--(average 5 cameras)
1.8 X 1.5 million = 2.7 million
● Middle income ( 30%)--80% will have cameras installed ( average 5 cameras)
4 X 1.35 million = 6.4 million
● High income (20%) --all will have cameras installed (average 10 cameras)
0.9 X 10 million= 9 million camera
18.1 million cameras for houses.
16|The Guessing Game
Total=​20.49 million CCTVs installed.
Now, if the number seems too large to be accurate, then some of our assumptions are
false. Maybe there are not enough households where CCTV is installed.
Also, note that we have assumed that all the shops are CCTV installed. That’s not a
correct assumption. Every office having CCTV is justified, but not every shop will have it.
Also, the average number of cameras that we thought are required in a house/shop etc.
may be incorrect. We need additional data to be sure. However, we need to demonstrate
to the interviewer that we thought of it.
Also, note that it is a very important guesstimate as it uses surreal segregation techniques
such as age split, economical split. Also, it uses a shortcut to estimate the number of
hospitals, schools etc.
17|The Guessing Game
CASE-9
Estimate the number of schools in Delhi.
Approach
Population of Delhi =1.5 crores-● 0-3 years --3%
● 3-18 years --30%-- 45 lacs-○ I. can afford education -- 90% --40 lacs approx
○ II. cannot afford education --10%
● 18-35 years --33%
● 35-60 years --25%
● 60 and above --8%
No. of class-1st to 12th, nursery I & II = 14 classes
No. of sections=10
No. of students/section=50
No. of students/school=50 X 10 X 14=7000
No. of schools=40,00,000/7000=​5700 schools(approx)
Follow-up question: Estimate the number of teachers teaching in schools.
Take the teacher to student ratio 40 students/teacher.
People attending school=40 lac
No. of teachers=40 lac/40=​1 lac
Follow-up question: Estimate the number of Govt. Schools in Delhi.
Govt School-● Run by State Govt
● Run by the Central Govt.
Delhi has-● 7 Parliamentary seats
● 70 Legislative seats/ 235 council wards
If we have an average of 10 schools/ward, the State Govt operates around 235 X 10 =
2350 schools.
The Central Government has 7 Parliamentary seats; if we have 70 schools/seats, then the
Central Government operates 70 X 7 = 490 schools.
Total Govt. schools = 2350 + 490 =​2840 schools.
No. of private schools = 5700 - 2840 =​2660 schools
18|The Guessing Game
Other follow-up questions can beEstimate the number of benches, chairs, fans etc. in schools located in Delhi.
For this, break down the no. of schools to no. of classrooms.
14 X 10 =​ 140 classes
Also, there are practice labs, so we assume 10 computer labs, 2 chemistry, 2 physics labs
and 10 more classrooms for drama, music, instrumentation and so on. ( Around 25 labs)
19|The Guessing Game
CASE -10
Estimate the number of hospitals in Delhi
Approach:
Hospitals
● State/Government-owned
● Private Hospitals
State/Government-owned
● Meant for everyone but generally targets the poor.
Private Hospitals
● Generally, target the reach.
Delhi Population:
(~1.5)crores
● Below Poverty Line: 10%= (~15)lakhs
● Low Middle Income: 45% = (~67.5)lakhs
● Middle Income: 35%= (~52.5)lakhs
● High Income: 10%= (~15)lakhs
1. Below Poverty Line
(~15)lakhs: Can’t afford private
2. Low Middle Income
(~67.5)lakhs: Can’t afford private
3. Middle Income
(~52.5)lakhs: (~25)lakhs can afford private(50%)
4. High Income
(~15)lakhs: All can afford private
Now assuming that we have a bed for every 1000 people
= (25,00,000+15,00,000)/1,000
=4000
Assuming 30 beds/Hospital = 4,000/30
= roughly 130 private Hospitals
Government-Owned Hospitals:
20|The Guessing Game
Delhi
Central
State
MCD
Central: 7 Constituencies
15 Central government Hospitals/ Constituency
= 15×7
= 105 Hospitals
State: 70 Legislative assembly seats
3 State government Hospitals/ Legislative seat
= 3×70
= 210 Hospitals
MCD:​ ​They generally have clinics and hence are not Hospitals
Number of government-operated Hospitals = 105+210 = 315 Hospitals
Number of Charitable Hospitals = 1/ Legislative assembly = 70 Hospitals
Total number of Hospitals = 120+315+70 = ​505 Hospitals
21|The Guessing Game
CASE -11
Estimate the number of ATMs in Delhi
ATMs
● Stand-alone ATMs
● Along with the bank branch
Population of Delhi = 1.5 crores and 25% aged-below
So 75% eligible to open an account
Say 90% of those eligible do have an account
= (9/10)×(3/4)×1.5 crores
~ 1 crore people (67.5% of 1.5 crore)
Now let there be a bank branch for every 5000 people, then
= (1,00,00,000)/5,000
= 2,000 bank branches
Say out of this 60 % do have an ATM along with the branch
=(60/100)×2,000
=1,200 ATMs
Stand Alone ATMs
● Metro Stations
● Markets
● Hospitals
● Others (like college area, residential area etc.)
Metro Stations
● 5 Metro routes
● Each has an approx 35 stations
● 2 ATMs at average on either side (there are two sides)
= 5×35×4
=700 ATMs
Hospitals
● One bed per thousand person
= 15,00,00,000/1,000
= 15,000
● 30 beds/ Hospital
= 15,000/30
= 500 Hospitals
● 3 ATMs/ Hospital
= 15,00 ATMs
22|The Guessing Game
70 constituencies, we take an average 2 market/ constituency and 2 ATMs/market
= 70×2×2
= 280 ATMs
Similar for residential areas, 2/constituency = 2×70
= 140 ATMs
Total of Stand-alone ATMs = 700+280+1500+140
= 2,760 ATMs
Total number of ATMs = 2760+1200
=​ 3,960 ATMs
23|The Guessing Game
CASE -12
Estimate the number of Band-Aids sold in India
Approach:
Band-Aids:
● Chemist Shops
● Hospitals
● Sports facilities
Assuming that we have a bed for every 10,000 persons and for a population of 120
crores, we have
= 120,00,00,000/10,000
=1,20,000 beds
And since we have a shortage of Hospitals, I assume that 5/6th of the total is always
occupied = 100k beds.
These patients will require, say 2 band-aids/day = 200k beds
But not all of them requires band-aids, so let 80% of them needs it
= 80% of 200k
= 160k band-aids
Also, if we assume that one hospital at an average has 20 beds, the
Total of hospitals = 100k/20= 50 Hospitals
Now if we assume that there exists a chemist shop for every 20k people, then
120,00,00,000/20,000
=60,000 shops
If each shop sells 15 band-aids at an average, then 15×60k=900k band-aids
India has approx 550 constituencies and if we take an average, 2 sports facilities per
constituencies, we have 2×550 = 1100 sports facilities.
If each sports facilities uses 50 band-aids a day
= 50×1.1k
=75k band-aids
24|The Guessing Game
Total number of Band-aids= 160k+1000k+900k+75k= 2135k=​ 2.135 million
25|The Guessing Game
CASE -13
Estimate the number of people travelling in Metro (Delhi Metro).
Approach​:
No. of Metro Routes=5
No. of metro lanes =2 per route =10 lanes
No. of stations = approx 40 per route = 40*10=400 metros
No. of coaches in a metro = 8 per metro rail = 8*400 = 3200 coaches
Frequency of metro = one metro/2 min = 30 metro /hr
Operating hours = 20 hours (approx)
=20*30*3200
=600*3.2K
=1920 K or 1.92 million
Now the maximum capacity of a metro coach = 200
​Occupancy of Delhi metro:
● 5-7 AM
● 7-11 AM
● 11AM-5PM
● 5-9 PM
● 9-1 AM
2hrs(60%)
4hrs(100%)
6hrs(70%)
4hrs(60%)
4hrs(60%)
Weighted average of occupancy = (1.2+4+4.2+4+2.4)*(1/20)
= 15.8/20= 80%
Daily Ridership of Delhi metro =0.192 million *200*80%
=0.192 million *160
= 30.70 million ridership
However, the question is the number of people travelling by Delhi metro and not daily
ridership.
26|The Guessing Game
So if we assume that a single person travels to and fro from Delhi metro, then we need to
count two ridership as one person. However, not everyone may do that. Suppose that 80%
of the total people use the metro for a round-trip journey and 20% for a single-sided
journey.
Therefore, average ridership per person= 0.8*2 +0.2*1 = 1.8
No. of people using Delhi Metro = 30.70/1.8 million
≈​17 million people
27|The Guessing Game
CASE -14
Estimate the number of copies of Sherlock Holmes sold in India this year.
Approach​:
Digital copy or hard copy? -------- (Hard copy only)
First hand or second hand? ---------- (First hand only)
Language -> regionally translates language or English ------------- (English only)
​Languages are spoken (1.2 crores):
● English speaking (25%)
● Non-English Speaking (75%)
300 million can speak/write or are proficient in the language
(We can also state that India has the second-largest pool of English speaking people, after
the U.S.)
​Economic Status:
●
●
●
●
Below poverty line (15%)
Low income (40%)
Middle income (30%)
High income (15%)
Therefore, 85% can afford a book -> 85% of 300 million = 255 million
Say 250 million
Age-wise split​:
●
●
●
●
●
Below 12 years (20%) ---- 5 million --- Barely can read
12-18 years (15%) ----37.5 million ---- 25% interested
18-30 years (30%) ---- 75 million ---- 20% interested
30-50 years (20%) ---- 50 million ---- 10% interested
50 and above (15%) ---- 37.5 million ----5% interested
Therefore, 5+15+10 million = 30 million includes in reading a novel.
Types of novels:
● Crime: 20%
28|The Guessing Game
●
●
●
●
Adventure: 15%
Biography: 15%
Romantic: 20%
Misc: 10%
Of crime genre, say, 15 % may be interested in
Buying a Sherlock Holmes novel.
i.e. 0.9 Million (interested)
Now some people, out of those interested, may
●
●
●
●
Have brought and read all of the novels.
Some will buy this year.
Some may not buy this now but can buy in the future.
Also, not everyone interested can buy a novel; they can rent it or buy a second
hand.
Interested Person (0.9 million)
● Rent: 40%
● Second Hand: 30%
● Purchase: 30%
Of all purchases (0.27 million)
● Brought and read: 25%
● Purchase: 15%
● Future Potential Buyers: 60%
​Therefore purchases = 0.27* 15 * (1/100)
=0.0405 Million
=​40.5K copies
29|The Guessing Game
CASE -15
Estimate the number of gulab jamuns sold in Delhi on a single day.
Approach​:
Gulab Jamun is sold at:
● Sweet shops
● Restaurants
● Snacks outlet (like BTW)
Now the sale of gulab jamun will be very different on a casual day compared to a festival
day like Diwali, Rakhi etc.
So we need to ask this to the interviewer for clarification. Let us for now. Assume that it
is a typical day.
There are seventy legislative assembly seats in Delhi. And if I was to recall my seat
(Karol Bagh), there are around 10 shops (which are branded) and another 25 shops which
are local.
Taking this as a standard, we have around 700 standard shops and 1750 local shops.
Considering daily average consumption of around 20 kg in branded shops and 10 kg in
local shops,
700*20 + 1750*10 = 14000 + 17500 = 31500 kg
Let a single kg of gulab jamun have 20 pieces,
31500*20 = ​630,000 pieces ----------------------- (A)
Again we have 70 legislative seats, and in my area, there are around 100 restaurants and
at least 20 hotels.
All the hotels will have gulab jamun on their menu, but only North Indian restaurants will
have gulab jamun on their menu.
30|The Guessing Game
Restaurants:
●
●
●
●
South Indian (30%)
North Indian (30%)
Chinese (15%)
Rest (15%)
Therefore, 45 restaurants and 20 hotels.
For 70 constitutions we have,
45*70 + 20*70 = 3150 restaurants and 1400 hotels.
Now, we assume that the hotel has at least 30 rooms with an average of 2 and out of the
10% may order Gulab jamun. (one per person).
Similarly, we assume that a hotel feeds 100 customers with an average customer size of 3
people and 10% of them order gulab jamun. (one per person)
3150*100*3*(1/10) and 1400*30*2*(1/10)
i.e. 94500 from restaurants and 8400 from hotels = 1
​ 02900 -------------- (B)
Snacks shops:
●
●
●
●
Pizza
Burgers
Indian snacks
Shakes
Only Indian snacks are required for estimation.
Again in Karol Bagh, I can safely say that there are 10 such Indian snacks shops which
serve around 15 people. Say only 10% of them have gulab jamun and we have 70
legislative seats.
70*10*150*(1/10)*1 = 1
​ 0500--------------(C)
Total​: 630,000 + 102900 + 10500 = ​743.4 K gulab jamuns per dayNote: H
​ ad it been
a festive day then we need to simply increase the number of gulab jamuns sold by the
sweet shops by several multiples.
31|The Guessing Game
CASE -16
Estimate the number of cars crossing Delhi-Gurgaon toll in a day:
Approach:
We will begin by estimating the # of people of different working classes who cross the toll
on a working day.
Population of Delhi = 1.5 crores
# of families (on an average scale consisting of 4 to 5 members each) = 45 Lakh
​Types of Occupation
Contribution
#
​ of people working
AGRICULTURE
10%
4.5 Lakh
SELF / BUSINESS
30%
13.5 Lakh
SERVICES
60%
27 Lakh
Now for a service family, we have
● 100% of Husbands working
● 60% of wives working
● 40% of children working ( assuming one child is working)
Therefore, Total # of working people = 2 X 27 Lakh = 54 Lakh
​Place of working
Contribution
#
​ of people working
GURGAON
40%
21.6 Lakh
DELHI
15%
8.1 Lakh
NOIDA
35%
18.9 Lakh
Also, there may be some people who may visit from Delhi to Gurgaon for schooling or
shopping purposes.
Assume the # of such people = 25 Lakh
32|The Guessing Game
Modes of transport
C
​ ontribution
# of people
Delhi Metro
40%
10 Lakh
Bus Services
15%
3.75 Lakh
Personal Vehicle
20%
5 Lakh
Cabs
●
Pool cab
●
Personal cab
25%
60%
40%
6.25 Lakh
3.75 Lakh
2.5 Lakh
Let the number of passengers in a cab pool be 3 on an average.
Therefore,# of such pool cabs = 3.75/3 = 1.25 Lakh
Therefore, Total # of cars =(# of pool cabs + # of personal vehicles + # of personal
cabs)
= 1.25 + 5 + 2.5 Lakh
=8
​ .75 Lakh
Note: T
​ his is the case for a working day. The situation will be different for a
weekend(Saturday or Sunday).
33|The Guessing Game
CASE -17
Estimate the revenue of an MCD outlet coming out from a burger sales:
Approach:
Type of sales
●
●
Online
Offline
Do we need to count both types of sales?
- No.Only the offline ones.
The MCD at any place has 3 billing mid-range counters.
Average time for preparing the burger and the bill for the customer is approximately 2
minutes.
Hence there are 30 burgers being prepared per hour per burger counter.
Distribution of sales
Timings
Percentage of customers
10 am - 1 pm
60%
1 pm - 4 pm
80%
4 pm - 7 pm
75%
7 pm - 11 pm
80%
What MCD sells?
Items
Percentage of sale
Fries/Wraps
20%
*Burgers
60%
34|The Guessing Game
Desserts/Drinks
20%
So 60% of the time, a sale at MCD implies the sale of a burger.
# of burgers,
= 0.6 X 30 ( 4 X 0.6 + 3 X 0.8 + 3 X 0.75 + 4 X 0.6 ) X 4
= 0.6 X 30 ( 2.4 + 2.4 + 2.25 + 2.4 ) X 4
= 0.6 X 30 (9.45) X 4
= 72 X 9.45
= 680 burgers
Types of burger
Percentage of sale
Actual Cost (INR)
Average Cost(INR)
Low priced
●
Veg
●
Non-veg
40%
60%
40%
40
50
45
Mid-range
●
Veg
●
Non-veg
30%
60%
40%
100
120
110
High priced
●
Veg
●
Non-veg
30%
60%
40%
150
170
160
The weighted average price of a burger,
= 0.4 X 45 +110 X 0.3 + 0.3 X 160
= 18 + 33 + 48
= 99 INR
/Therefore, Total Revenue = 680 X 99 INR
=6
​ 7,320 INR
Note:
The sale/occupancy shall vary depending upon whether it is a working day or a weekend.
Also, if the total revenue was to be estimated, then the revenue from
fries/wraps/desserts/meals are required to be taken care of. The choice of 4 counters was
very random.
35|The Guessing Game
It is a good idea to divide the meal as veg & non-veg when we are considering Indian
consumers. This may not be required in the international market(the US or Europe)
Also, the question can be further extended to calculate the MCD from Delhi region. For
this, simply assume 1 to 2 stores per legislative assembly. This counts for nearly 90-140
stores.
The same set of questions can be extended to estimate the revenue of a restaurant. But
you need to ask whether the restaurant operates in the Budget, Mid-tier or Premium
segment and then proceed.
36|The Guessing Game
CASE -18
Estimate the number of televisions and refrigerators sold in Delhi in a year
(Also estimate the revenue) :
Approach:
Population of Delhi = 1.5 crores
# of families (on an average scale consisting of 4 to 5 members each) = 45 Lakh
Economic
distribution
Contribution
# of people
Average # of refrigerators
Below poverty line
15%
6.75 Lakh
0
Low income
40%
18 Lakh
1
Middle income
30%
13.5 Lakh
1.2
High income
15%
6.75 Lakh
1.5
Weighted average = 0 X 0.15 + 1 X 0.4 + 1.2 X 30 + 1.5 X 0.15
= 0.4 + 0.36 + 0.225
= 0.965
Therefore, # of refrigerators in Delhi households = 0.965 X 45 Lakh
= 43 Lakh
Average lifespan of a refrigerator = 15 years
Therefore,units sold annually due to replacement = 43 / 15 = 2.9 Lakh
However, there are also first-time buyers. Those people who bought for the first-time will
be those who have been uplifted from poverty. Say 5 % of the people are uplifted from
poverty.
= 6.75 X ( 1 / 20 ) Lakh
= 32,250 INR
Therefor,Total sales annually = 2.9 + (0.32250 ~ 0.32)
= 3.22 Lakh
Other than this , refrigerators are bought for commercial purposes as well.
Commercial Use:
37|The Guessing Game
● Hotels
● Restaurants
● Storage Facilities
However, they are generally not asked to be estimated.
Revenue generated by refrigerator sales(considering different types of refrigerators):
Types of refrigerator
Percentage of the market
Average unit price
Entry-level
40%
15K
Mid-level
40%
40K
High/premium level
20%
75K
Total Revenue = 3.22 X ( 0.4 X 15K + 0.4 X 40K + 0.2 X 75K ) Lakh
= 3.22 X ( 6K + 16K + 15K) Lakh
= 3.22 Lakh X 37K
= 120K Lakh
= 120 crores (roughly $2 billion)
The second part is to estimate the # of televisions sold in Delhi.
Distribution of televisions:
● Hospitals
● Hotels
● Offices
● Personal Use
● Residential
● Commercial(e.g. stores)
Population of Delhi = 1.5 crores
# of families (on an average scale consisting of 4 to 5 members each) = 45 Lakh
Economic situation
Contribution
Average # of TV
Percentage of
families
38|The Guessing Game
Below poverty line
15%
0
6.75 Lakh
Low income
40%
1
18 Lakh
Mid income
30%
2
13.5 Lakh
High income
15%
3
6.75 Lakh
Total # of TVs in households = 0 X 6.75 + 1 X 18 + 2 X 13.5 + 3 X 6.75 Lakh
= 65.25 Lakh
The average lifespan of a TV = 10 years
Therefore,units sold annually due to replacement = 65.25 / 10 = 6.525 Lakh
Economic activity
Number of paracetamol tablets sold in Delhi
Places where they are sold
● Hospitals
● Chemist shops
Delhi (7 parliament constituency) ➔ Legislative
70 constituency ➔ 235 Wards
In my ward, I can estimate that there are roughly 20
chemist shops.
Therefore, No. of chemist shops = 235 X 20 = 4,700
shops.
Each shop on an average may sell ten shops (100
tablets).
Therefore, tablets sold = 4,700 X 100 = 470,000 or
470k tablets.
Population of Delhi = 1.5 Crore
Let there be a bed for every 5000 persons =
15,000,000/5,000 = 3,000 beds.
Let there be 30 beds per hospital = 3,000/30 = 100
hospitals
39|The Guessing Game
If at an average, a hospital sells 100 strips (1,000
tablets), then tablets sold by hospital = 100 X 1,000 =
100k.
Total number of tablets sold = 470k+100k = 570k
tablets.
Note, parameters like several beds or 1,000 persons or
so on are also general parameters which can help us to
determine the quality of health-care in the country.
If the question was several paracetamol tablets sold in
India, then take that India has approx 550 constitutions
➔ Approx 5,000 state counselling seats ➔ 35,000
municipal wards ➔ 20 chemist shops/ward = 700k
chemist shops.
Similarly, Delhi has a better medical facility than the
national average. Hence we can take 10,000 persons/bed
to estimate hospitals.
Further, notice that these variations are in the general
present for developing nations.
Developed nations do not have these many disciplines in
the data.
If we, for example, had to estimate for the state of
California, then.
The US population ➔ 50 states, the average population
per state = 7 million.
But since California is an industrial state and near the
coastline, it’s population will be slightly higher than the
average/mean value. So, begin by taking 8 million
citizens.
Also, we can estimate that one bed/500 persons may be
available in California or one bed/1000 persons, as it’s
medical facilities will be better than Delhi.
40|The Guessing Game
Agriculture/Forestry
10%
Business
30%
Service
60%
Let half of the females be working = 67.5 Lakh
Therefore, people working in service = 39 Lakh
Assuming 500 persons working per office.
Average size of office = 39 / 500 Lakh = 7800 offices
Average # of TV in offices = 7800 X 100 = 7.8 Lakh
Similarly let there be a bed for every 10,000 persons in the population.
# of beds = 1.5 crore / 10,000 = 1500 beds
Average # of beds per hospital = 20
# of hospitals = 1500 / 20 = 75 hospitals
Average # of TV per hospital = 100
Therefore, Total # of TVs in hospitals = 7500
Therefore, Total # of TVs = 6.525 Lakh + 7.8 Lakh + 7500
=​ 14.395 Lakh
41|The Guessing Game
CASE - 19
​The number of iPhones sold in India :
Approach ​:
Number of mobile users = 100 Crores
100 Crores :
●
●
2G/3G Network (60 Crores Users) (60%)
4G Network (40 Crores users) (40%)
Smart Phones :
●
Budget (50 Crores Users) (50%)
●
Mid-level (10 Crores Users) (25%)
●
Upper mid (6 Crores Users) (15%)
●
Premium (4 Crores Users) (10%)
The average life of a smartphone = 3 Years
So, 4/3 = 1.33 Crores phones
Premium phones :
●
Samsung (26 Lacs Users) (20%)
●
HTC (15%)
●
LG (10%)
●
Chinese (35%)
●
Apple (26 Lacs Users) (20%)
The average income of Delhi = 126,000Rs annually
The average income of India = 65,000Rs annually
So, Delhi has 2X more wealth.
The population of Delhi = 1.5 Crore
The population of India = 120 Crore
So, 120/1.5 = 80
Also, Delhi has two times more wealth so that it will be 40
Number of iPhones sold in Delhi = 26/40 Lacs = 65,000 iPhones
42|The Guessing Game
Sales :
●
Q1 (30%) (New year)
●
zQ2 (20%) (Relatively low sale period)
●
Q3 (20%) (Relatively low sale period)
●
Q4 (30%) (Diwali) (⅓ rd of the total comes in the Diwali period) (say)
●
So, iPhones sold in Delhi in Diwali sale = 65,000 X 30/100 X ⅓ = 6,500
iPhones.
The question can be further extended to estimate the number of iPhones sold online v/s
offline.
Also, instead of iPhones, we can be asked to estimate the sale of a new Samsung/Google
phone.
We can also be asked to estimate the revenue generated by a telecom company/ telecom
industry by offering only voice & data services.
The economic distribution for Delhi, Mumbai, Chennai, Kolkata, Hyderabad, etc. will be
similar​.
Delhi
●
●
●
●
Budget phones (30%)
Low-mid level (30%)
Mid-level (20%)
High level (20%)
India
●
●
●
●
Budget (40%) (Dominated by Chinese vendor & Samsung)
Low-mid (30%) (Dominated by Chinese vendor & Samsung)
Mid (20%) (Highly fragmented by Chinese player)
High end (10%) (Dominated by Samsung/Apple followed by Chinese vendor)
43|The Guessing Game
CASE-20
A number of paracetamol tablets sold in Delhi :
Approach :
Places where they are sold
● Hospitals
● Chemist shops
Delhi (7 parliament constituency) ➔ Legislative 70 constituency ➔ 235
Wards:
In my ward, I can estimate that there are roughly 20 chemist shops.
Therefore, No. of chemist shops = 235 X 20 = 4,700 shops.
Each shop on an average may sell ten shops (100 tablets).
Therefore, tablets sold = 4,700 X 100 = 470,000 or 470k tablets.
Population of Delhi = 1.5 Crore
Let there be a bed for every 5000 persons = 15,000,000/5,000 = 3,000 beds.
Let there be 30 beds per hospital = 3,000/30 = 100 hospitals
If at an average, a hospital sells 100 strips (1,000 tablets), then tablets sold by hospital =
100 X 1,000 = 100k.
Total number of tablets sold = 470k+100k = 570k tablets.
Note:​ Parameters like several beds or 1,000 persons or so on are also general parameters
which can help us to determine the quality of health-care in the country.
If the question was several paracetamol tablets sold in India, then take that India has
approx 550 constitutions ➔ Approx 5,000 state counselling seats ➔ 35,000 municipal
wards ➔ 20 chemist shops/ward = 700k chemist shops.
44|The Guessing Game
Similarly, Delhi has a better medical facility than the national average. Hence we can take
10,000 persons/bed to estimate hospitals.
Further, notice that these variations are in the general present for developing nations.
Developed nations do not have these many disciplines in the data.
If we, for example, had to estimate for the state of California, then.
The US population ➔ 50 states, the average population per state =​ 7 million.
But since California is an industrial state and near the coastline, it’s population will be
slightly higher than the average/mean value. So, begin by taking 8 million citizens.
Also, we can estimate that one bed/500 persons may be available in California or one
bed/1000 persons, as it’s medical facilities will be better than Delhi.
45|The Guessing Game
CASE -21
Estimate the number of lakes in the world:
Approach :
​
Radius of the Earth=6400 km=2​6 X100
km
​
​
​
Therefore, the surface area of the Earth=4 X 3.14 X 2​6 X
2​6 X
100 X 100km​2 =
12.56
2
X 4,096 X 10,000km​
Assuming Earth to be a perfect sphere ~ 510 million km​2​.
Earth:● Water(70%) (357.5million km​2​)
● Land(30%) (152.5 million km​2​)
98% of the water on earth is in the ocean and sea. That is approximately 350 million
square kilometres.
And the rest 2 %, i.e., 7 million square kilometres.
Out of the total freshwater, 98% is in the form of glaciers(6.84 million square kilometres).
The remaining 2% of the freshwater(0.16 million square kilometres) is in the form of
rivers, lakes and ponds.
Out of this 0.16 million square kilometres 85% is in the form of rivers(119,000km​2​), 10%
in the form of lakes(14,000km​2​) and 5% in the form of ponds(7,000km​2​) .
Now let us assume that the average side of a lake is 1,000mt X 100mt = 0.01km​2​.
Total no. of lakes = 14,000 X 100= 14 lakh lakes
(According to Google, we have approximately 20 lakh lakes. But these can be both
saltwater and freshwater lakes.)
46|The Guessing Game
Also, we can say that these lakes are natural lakes. There may be some artificial lakes
made by human beings for their use.
Lakes can be classified as:● Freshwater lakes
● Saline Lakes
Lakes can also be classified as:● Natural
● Man-made (or) Artificial
47|The Guessing Game
CASE - 22
Estimating the size of the tyre industry in India in 2020 :
Approach :
The population of India = 125 crores with the average family size of 4 to 5 = 30 crore to
25 crore
Say we take 27 crore families in India.
Low income –
​ No one will own an SUV
Mid/High income​ – These people may own a new/used SUV.
​SUV by the high-end people​= 2.7 crores (0.5+0.6=0.3)
2.7crore*1.4=3.5 crores
Assuming that the average life of an SUV is 15 years, we have
sold
350/15 lac SUV
Approx. 2 million SUV = 20 lac SUV
So we have,
26.6 lakhs new SUV sold in India in 2020 and a total of 4.2 crore SUV in the country.
Also, let us assume that 12% of the new SUVs sold in India (brought by Indian) are
explored abroad.
Therefore, the new SUV requires 5 tyres
=
150 lakh tyres for new SUVs.
48|The Guessing Game
(4tyre+1extra)
Let every one out of five cars require a tyre replacement in a year.
è 350/5*1=70 lakh replacement tyres.
Total tyres = 150lakh+70lakh
=
220lakh
( over 22 million tyre)
Revenue of the SUV tyre industry – Let the average price of the tyre be 10,000.
220 million * 10,000
= Rs. 220 billion
Revenue in = $ 220/60 billion = ​$ 3.67 billion
49|The Guessing Game
CASE- 23
The number of roses sold in Delhi on 14​th​ February :
Approach :
Delhi population = 1.5 crore
Now everyone will not celebrate Valentine day by giving a rose.
Therefore, approximately 1.5 lac roses can be sold on 14​th​ February in Delhi.
180K Roses.
Follow up question -> Estimate the number of roses sold by a flower vendor in Delhi on
14​th​ February.
​A-- 350 Vendors (shops)
But during the 14​th​ February, various street vendors also sell roses.
They are primary at metro stations and markets.
The number of metro stations = five metro lines * 40 average number of stations per line.
B -- 200 stations
At an average 3 vendors per station (one vendor /entry or exit gate) = 600 vendors.
50|The Guessing Game
Again 70 constituencies, taking two markets per constituency, approximately 150
markets.
5 vendors per market => C-- 750 vendors
Total vendors = 350+600+750
= 1800 Vendors
Average number of roses sold per vendor = 150000/1800 = 83 rose
Average revenue =
average price * unit sold
(taking the average = 25*83
price to be 25
rupees per rose)
= 8300/4
=2
​ 075 /vendor
51|The Guessing Game
CASE-24
The number of footballs sold in India:
Approach :
Population of India = 125 crores.
Now,14 classes for ten sections with 50 students each.
⇨ The average number of students in a school=14*10*50=7000
.:. The number of schools=250000000/7000=35700 schools.
Say 80%, of these school, have football facility, and that they order ten football each in a
calendar year
=35700*10*0.8=295600
=>2.956 lac
…………………………(a)
Out of 18.75 crore people who can pursue higher education, say 40% of them pursue a
college degree.
(Assuming that many people in rural areas are deprived of getting higher education ).
Number of people pursuing a college=18.75*0.4 crore
=7.5 crore
Assuming that at an average a college hosts 5000 persons, the average number of
colleges= 75000000/5000=15000 colleges.
Assuming that each college orders 20 footballs and 90% of them have a football-playing
facility.
=>15000*0.9*10=135000 or 1.35 lac​………………(b)
52|The Guessing Game
Say 90% of the states have a state football team and each state has at an average 30
clubs/sports facilities where football is being played. And each club purchases 20 footballs
annually.
.:. 30*35*0.9*20
=2100*9
=18900
Assume 20k as with the national/state team.
Also Indian Super League, we have around ten teams, each playing two with the other,
followed by elimination rounds.
Each match requires two balls and approx 20 for making the players practice.
.:.(45+5)*22=1100 footballs.
Total number of footballs for sports club/state and national
team=1100+18900+1100=21100 footballs.
………………………(c)
.:. Total number of footballs =a+b+c
=295k+135k+21.1k
=441.1 k footballs
Or 4
​ .411 lac footballs​.
53|The Guessing Game
CASE - 25
Number of students attending 10th/12th/college in India :
Approach :
Population of India = 125 crores
Age - wise split:
a. Below 18 years - 25% - 31.25 crores
b. 18 - 25 years - 15% - 18.75 crores
c. 25 - 40 years - 25% - 31.25 crores
d. 40 - 60 years - 20% - 25 crores
e. 60 years & above - 15% - 18.75 crores
Now, if we assume a uniform distribution of people in under 18 year age group, we have
31.25 ​÷ 18 crore people in 16th & 18th year of age
1.73 crore people
Economic Status:
a. Below poverty line - 15% - can’t study 10th, 12th, college due to affordability.
b. Low - income - 40% - many in rural areas may not be able to study 12th class due
to economic reasons. Many more can’t go to college.
c. Mid - income - 35% - Everyone goes to 10th, 12th. Almost 80% go to college
d. High Income - 10% - Everyone goes to 10th, 12th & college.
54|The Guessing Game
10th class
0% from BPL + 90% from Low income + 100% from mid-income + 100% from
high-income
1.40 crores
12th class
0% from BPL + 70% from Low income + 100% from mid-income + 100% from
high-income
1.10 crores
College
Also, note that for higher education, though everyone in the high-income category can
afford a college education in India, not everyone goes to Indian university. Some may go
abroad as well and hence 70%.
0% from BPL + 20% from Low income + 50% from mid-income + 70% from high
income
0.325 crores
Total = 0.325 X 18.75 X 20% (These are those who want to go to college and do not
have family business to support)
1.50 crores
55|The Guessing Game
CASE - 26
The number of golf balls that can fit in the room :
Approach :
Assume the room to be approximately 4m wide & 6m long. The height of the room can be
assumed to be 4m.
Volume of the room = 4 X 6 X 4 = 960k cm^2
Let the average diameter of a golf ball is assumed to be 5cm
Volume of golf ball = 3.14 X 4 X 5 X 5 X 5 ​÷ 3​ = 523.30 cm^
Way I
A cube of volume radius^3 packs the golf ball
Number of balls = 960 X 1000 ÷
​ 125 = 7680 golf balls
Way II
A packing arrangement like Face Centred Cubic (FCC) of crystals
The volume (2 X radius / √3)^3 holds two golf balls.
Number of balls = 7680 ÷ 0.77 = 9600 golf balls
56|The Guessing Game
Alternate Question ​- H
​ ow many golf balls can fit in a Boeing 747 plane.
Assume that the plane consists of a pyramid (height 5m, base 10m X 3m) at the head
followed by a cuboid (30m X 3m X 10m)
Volume of the plane = 0.33 X area of base X height + length X breadth X height
The volume of the plane = 9500k cm^2
Volume occupied by a. Cockpit, engine, seats & other critical infrastructure = 30% = 2580k cm^2
b. Free / unoccupied = 70% = 6650k cm^2
Way I
Number of golf balls = 6650 X 1000 / 125 = ​53,200 golf balls
Way II
Number of golf balls = 6650 X 1000 / (0.77 X 125) = ​69,090 golf balls.
CASE - 27
Estimate the number of hair on your scalp:
Approach :
Estimating area of the head a. Assuming head to be rectangular
Assuming that the width (of the forehead) is 10cm & the length is 15 cm
Area = 150 cm^2
Assuming 80% of the scalp is covered with hair
Effective area = 150 - 30 = 120 cm^2
Assuming the thickness of hair to be 0.2 cm, we have
Number of hair = 120 / 0.2 = 6
​ 00 hair
b. Assuming it to be curved (half of the curved surface area of the head)
Assuming that radius is 5 cm
Area = 167 cm^2
Assuming 80% of the scalp is covered with hair
Effective Area = 167 - 33.4 = 133.6cm^2
Assuming the thickness of hair to be 0.2 cm, we have
Number of hair = 133.6 / 0.2 =​ 668 hairs.
57|The Guessing Game
CASE 28
Estimate the number of people travelling in Metro (Delhi Metro)
Approach​:
No. of Metro Routes=5
No. of metro lanes =2 per route =10 lanes
No. of stations = approx 40 per route = 40*10=400 metros
No. of coaches in a metro = 8 per metro rail = 8*400 = 3200 coaches
Frequency of metro = one metro/2 min = 30 metro /hr
Operating hours = 20 hours (approx)
=20*30*3200
=600*3.2K
=1920 K or 1.92 million
Now the maximum capacity of a metro coach = 200
58|The Guessing Game
​Occupancy of Delhi metro:
●
●
●
●
●
5-7 AM
7-11 AM
11AM-5PM
5-9 PM
9-1 AM
2hrs(60%)
4hrs(100%)
6hrs(70%)
4hrs(60%)
4hrs(60%)
Weighted average of occupancy = (1.2+4+4.2+4+2.4)*(1/20)
= 15.8/20= 80%
Daily Ridership of Delhi metro =0.192 million *200*80%
=0.192 million *160
= 30.70 million ridership
However, the question is the number of people travelling by Delhi metro and not daily
ridership.
So, if we assume that a single person travels to and fro from Delhi metro, then we need to
count two ridership as one person.
However, not everyone may do that. Suppose that 80% of the total people use the metro
for a round-trip journey and 20% for a single-sided journey.
Therefore, average ridership per person= 0.8*2 +0.2*1 = 1.8
No. of people using Delhi Metro = 30.70/1.8 million
​≈17 million people
59|The Guessing Game
CASE 29
Estimate the number of copies of Sherlock Holmes sold in India, this
year
Assumptions​:
Digital copy or hard copy? -------- (Hard copy only)
First hand or second hand? ---------- (First hand only)
Language -> regionally translates language or English ------------- (English only)
No. of languages spoken​: 1.2 crores
● English speaking (25%)
● Non-English Speaking (75%)
300 million can speak/write or are proficient in the language.
(We can also state that India has the second-largest pool of English speaking people, after
the U.S.)
Economic Status:
●
●
●
●
Below poverty line (15%)
Low income (40%)
Middle income (30%)
High income (15%)
Therefore, 85% can afford a book -> 85% of 300 million = 255 million
Say 250 million
Age-wise split:
●
●
●
●
●
Below 12 years (20%) ---- 5 million --- Barely can read
12-18 years (15%) ----37.5 million ---- 25% interested
18-30 years (30%) ---- 75 million ---- 20% interested
30-50 years (20%) ---- 50 million ---- 10% interested
50 and above (15%) ---- 37.5 million ----5% interested
Therefore, 5+15+10 million = 30 million includes reading a novel.
60|The Guessing Game
Types of novels:
●
●
●
●
●
Crime: 20%
Adventure: 15%
Biography: 15%
Romantic: 20%
Misc: 10%
Of crime genre, say, 15 % may be interested in
Buying a Sherlock Holmes novel.
i.e. 0.9 Million (interested)
Now some people, out of those interested, may
● Have brought and read all of the novels.
● Some will buy this year.
● Some may not buy this now but can buy in the future.
●
●
●
●
Also, not everyone interested can buy a novel, the interested​ person ​(0.9 million)
Rent: 40%
Second Hand: 30%
Purchase: 30%
​Of all purchases (0.27 million)
● Brought and read: 25%
● Purchase: 15%
● Future Potential Buyers: 60%
Therefore purchases =
​ 0.27* 15 * (1/100)
=0.0405 Million=​40.5K copies
61|The Guessing Game
CASE 30
Estimate the number of gulab jamuns sold in Delhi on a single day
Approach​:
Gulab Jamun is sold at:
● Sweet shops
● Restaurants
● Snacks outlet (like BTW)
Now the sale of gulab jamun will be very different on a casual day compared to a festival
day like Diwali, Rakhi, etc.
So we need to ask the interviewer for clarification.
Let us for now, assume that it is a normal day.
There are seventy legislative assembly seats in Delhi. And if I was to recall my seat
(Karol Bagh) there are around 10 shops (which are branded) and another 25 shops which
are local.
Taking this as a standard, we have around 700 standard shops and 1750 local shops.
Considering daily average consumption of around 20 kg in branded shops and 10 kg in
local shops,
700*20 + 1750*10 = 14000 + 17500 = 31500 kg
Let a single kg of gulab jamun have 20 pieces,
31500*20 = ​630,000 pieces ----------------------- (A)
Again we have 70 legislative seats and in my area, there are around 100 restaurants and
at least 20 hotels.
All the hotels will have gulab jamun on their menu but only North Indian restaurants will
have gulab jamun on their menu.
Restaurants:
62|The Guessing Game
●
●
●
●
South Indian (30%)
North Indian (30%)
Chinese (15%)
Rest (15%)
Therefore, 45 restaurants and 20 hotels.
For 70 constitutions we have,
45*70 + 20*70 = 3150 restaurants and 1400 hotels.
Now, we assume that the hotel has at least 30 rooms with an average of 2, and out of
them, 10% may order Gulab jamun. (one per person).
Similarly, we assume that a hotel feeds 100 customers with an average customer size of 3
people and 10% of them order gulab jamun. (one per person)
3150*100*3*(1/10) and 1400*30*2*(1/10)
i.e. 94500 from restaurants and 8400 from hotels = 1
​ 02900 -------------- (B)
Snacks shops:
●
●
●
●
Pizza
Burgers
Indian snacks
Shakes
Only Indian snacks are required for estimates.
Again in Karol Bagh, I can safely say that there are 10 such Indian snack shops that
serve around 15 people. Say only 10% of them have gulab jamun and we have 70
legislative seats.
70*10*150*(1/10)*1 = 1
​ 0500--------------(C)
Total : 630,000 + 102900 + 10500 = 7
​ 43.4 K gulab jamuns per day
​ ote:​ ​Had it been a festive day then we need to simply increase the number of gulab
N
jamuns sold by the sweet shops by several multiples.
63|The Guessing Game
CASE 31
Estimate the number of cars crossing Delhi-Gurgaon toll in a day:
Approach:
We will begin by estimating the no. of people of different working classes who cross the
toll on a working day.
Population of Delhi = 1.5 crores
No. of families (on an average scale consisting of 4 to 5 members each) = 45 Lakh
Types of Occupation
Contribution
No. of people
working
AGRICULTURE
10%
4.5 Lakh
SELF / BUSINESS
30%
13.5 Lakh
SERVICES
60%
27 Lakh
Now for a service family, we have
● 100% of Husbands working
● 60% of wives working
● 40% of children working ( assuming one child is working)
Therefore, Total no. of working people = 2 X 27 Lakh = 54 Lakh
​Place of working
Contribution
No. of people
working
GURGAON
40%
21.6 Lakh
DELHI
15%
8.1 Lakh
NOIDA
35%
18.9 Lakh
64|The Guessing Game
Also, there may be some people who may visit from Delhi to Gurgaon for schooling or
shopping purposes.
Assume the no. of such people = 25 Lakh
Modes of transport
C
​ ontribution
No. of
people
Delhi Metro
40%
10 Lakh
Bus Services
15%
3.75 Lakh
Personal Vehicle
20%
5 Lakh
Cabs
●
Pool cab
●
Personal cab
25%
60%
40%
6.25 Lakh
3.75 Lakh
2.5 Lakh
Let the number of passengers in a pool cab be 3 on an average.
Therefore,no. of such pool cabs = 3.75/3 = 1.25 Lakh
Therefore, Total no. of cars =(No. of pool cabs + No. of personal vehicles + No. of
personal cabs)
= 1.25 + 5 + 2.5 Lakh
=8
​ .75 Lakh
Note: T
​ his is the case for a working day. The situation will be different for a
weekend(Saturday or Sunday).
65|The Guessing Game
CASE 32
Estimate the revenue of an MCD outlet coming out from a burger sales
Approach​:
Type of sales:
● Online
● Offline
Do we need to count both types of sales?
- No.Only the offline ones.
The MCD at any place has 3 billing/servicing counters.
Average time for preparing the burger and the bill for the customer is approximately 2
minutes
Hence there are 30 burgers being prepared per hour per burger counter.
Distribution of sales
Timings
Percentage of customers
10 am - 1 pm
60%
1 pm - 4 pm
80%
4 pm - 7 pm
75%
7 pm - 11 pm
80%
What does MCD sell?
Items
Percentage of sale
Fries/Wraps
20%
66|The Guessing Game
Burgers
Desserts/Drinks
1. 60%
20%
So 60% of the time, a sale at MCD implies the sale of a burger.
No. of burgers,
= 0.6 X 30 ( 4 X 0.6 + 3 X 0.8 + 3 X 0.75 + 4 X 0.6 ) X 4
= 0.6 X 30 ( 2.4 + 2.4 + 2.25 + 2.4 ) X 4
= 0.6 X 30 (9.45) X 4
= 72 X 9.45
= 680 burgers
Types of burger
Percentage of sale
Actual Cost (INR)
Average Cost(INR)
Low priced
●
Veg
●
Non-veg
40%
60%
40%
40
50
45
Mid-range
●
Veg
●
Non-veg
30%
60%
40%
100
120
110
High priced
●
Veg
●
Non-veg
30%
60%
40%
150
170
160
The weighted average price of a burger,
= 0.4 X 45 +110 X 0.3 + 0.3 X 160
= 18 + 33 + 48
= 99 INR
Therefore, Total Revenue = 680 X 99 INR
=6
​ 7,320 INR
Note​:
67|The Guessing Game
The sale/occupancy shall vary depending upon whether it is a working day or weekend.
Also, if the total revenue was to be estimated then the revenue from
fries/wraps/desserts/meals are required to be taken care of.
The choice of 4 counters was very random.
It is a good thought to divide the meal as veg & non-veg when we are considering Indian
consumers. This may not be required in the international market(the US or Europe)
Also, the question can be further extended to calculate the MCD from Delhi region. For
this, simply assume 1 to 2 stores per legislative assembly. This counts for nearly 90-140
stores.
The same set of questions can be extended to estimate the revenue of a restaurant. But
you need to ask whether the restaurant operates in the Budget, Mid-tier or Premium
segment and then proceed.
68|The Guessing Game
CASE 33
Estimate the number of televisions and refrigerators sold in Delhi in a year
(Also estimate the revenue)
Approach​:
Population of Delhi = 1.5 crores
no. of families (on an average scale consisting of 4 to 5 members each) = 45 Lakh
Economic
distribution
Contribution
no. of people
Average no. of refrigerators
Below poverty line
15%
6.75 Lakh
0
Low income
40%
18 Lakh
1
Middle income
30%
13.5 Lakh
1.2
High income
15%
6.75 Lakh
1.5
Weighted average = 0 X 0.15 + 1 X 0.4 + 1.2 X 30 + 1.5 X 0.15
= 0.4 + 0.36 + 0.225
= 0.965
Therefore, no. of refrigerators in Delhi households = 0.965 X 45 Lakh
= 43 Lakh
Average lifespan of a refrigerator = 15 years
Therefore,units sold annually due to replacement = 43 / 15 = 2.9 Lakh
However, there are also first-time buyers. Those people who bought for the first-time will
be those who have been uplifted from poverty. Say 5 % of the people are uplifted from
poverty.
69|The Guessing Game
= 6.75 X ( 1 / 20 ) Lakh
= 32,250 INR
Therefor,Total sales annually = 2.9 + (0.32250 ~ 0.32)
= 3.22 Lakh
Other than this , refrigerators are bought for commercial purposes as well.
COMMERCIAL USE
● Hotels
● Restaurants
● Storage Facilities
However, they are generally not asked to be estimated.
Revenue generated by refrigerator sales(considering different types of refrigerators):
Types of refrigerator
Percentage of the market
Average unit price
Entry-level
40%
15K
Mid-level
40%
40K
High/premium level
20%
75K
Total Revenue = 3.22 X ( 0.4 X 15K + 0.4 X 40K + 0.2 X 75K ) Lakh
= 3.22 X ( 6K + 16K + 15K) Lakh
= 3.22 Lakh X 37K
= 120K Lakh
= 120 crores (roughly $2 billion)
The second part is to estimate the no. of televisions sold in Delhi
​Distribution of televisions
●
●
●
●
Hospitals
Hotels
Offices
Personal Use
70|The Guessing Game
-Residential
-Commercial( eg. stores)
Population of Delhi = 1.5 crores
no. of families (on an average scale consisting of 4 to 5 members each) = 45 Lakh
Economic situation
Contribution
Average no. of
TV
Percentage of families
Below poverty line
15%
0
6.75 Lakh
Low income
40%
1
18 Lakh
Mid income
30%
2
13.5 Lakh
High income
15%
3
6.75 Lakh
Total no. of TVs in households = 0 X 6.75 + 1 X 18 + 2 X 13.5 + 3 X 6.75 Lakh
= 65.25 Lakh
The average lifespan of a TV = 10 years
Therefore,units sold annually due to replacement = 65.25 / 10 = 6.525 Lakh
Economic activity
Contribution
Agriculture/Forestry
10%
Business
30%
Service
60%
Let half of the females be working = 67.5 Lakh
Therefore, people working in service = 39 Lakh
Assuming 500 persons working per office.
Average size of office = 39 / 500 Lakh = 7800 offices
Average no. of TV in offices = 7800 X 100 = 7.8 Lakh
71|The Guessing Game
Similarly, let there be a bed for every 10,000 persons in the population.
no. of beds = 1.5 crore / 10,000 = 1500 beds
Average no. of beds per hospital = 20
no. of hospitals = 1500 / 20 = 75 hospitals
Average no. of TV per hospital = 100
Therefore, Total no. of TVs in hospitals = 7500
Therefore, Total no. of TVs = 6.525 Lakh + 7.8 Lakh + 7500= 1
​ 4.395 Lakh
CASE 34
Number of iPhones sold in India
Approach​:
Number of mobile users = 100 Crores
100 Crores​ :
●
●
2G/3G Network (60 Crores Users) (60%)
4G Network (40 Crores users) (40%)
Smart Phones​ :
●
●
●
●
Budget (50 Crores Users) (50%)
Mid-level (10 Crores Users) (25%)
Upper mid (6 Crores Users) (15%)
Premium (4 Crores Users) (10%)
The average life of a smartphone = 3 Years
So, 4/3 = 1
​ .33 Crores​ phones
Premium phones​ :
●
●
●
●
●
Samsung (26 Lacs Users) (20%)
HTC (15%)
LG (10%)
Chinese (35%)
Apple (26 Lacs Users) (20%)
The average income of Delhi = 126,000Rs annually
The average income of India = 65,000Rs annually
72|The Guessing Game
So, Delhi has 2X more wealth.
The population of Delhi = 1.5 Crore
The population of India = 120 Crore
So, 120/1.5 = 80
Also, Delhi has two times more wealth, so it will be 40
Number of iPhones sold in Delhi = 26/40 Lacs = 65,000 iPhones
Sales​ :
●
Q1 (30%) (New year)
●
Q2 (20%) (Relatively low sale period)
●
Q3 (20%) (Relatively low sale period)
●
Q4 (30%) (Diwali) (⅓ rd of the total comes in the Diwali period) (say)
So, iPhones sold in Delhi in Diwali sale = 65,000 X 30/100 X ⅓ = 6,500 iPhones.
The question can be further extended to estimate the number of iPhones sold online v/s
offline.
Also, instead of iPhones, we can be asked to estimate the sale of a new Samsung/Google
phone.
We can also be asked to estimate the revenue generated by a telecom company/ telecom
industry by offering only voice & data services.
The economic distribution for Delhi, Mumbai, Chennai, Kolkata, Hyderabad etc. will be
similar.
Delhi
●
●
●
●
Budget phones (30%)
Low-mid level (30%)
Mid-level (20%)
High level (20%)
India
●
●
●
●
Budget (40%) (Dominated by Chinese vendor & Samsung)
Low-mid (30%) (Dominated by Chinese vendor & Samsung)
Mid (20%) (Highly fragmented by Chinese player)
High end (10%) (Dominated by Samsung/Apple followed by Chinese vendor)
73|The Guessing Game
CASE 35
Number of paracetamol tablets sold in Delhi
Approach​:
Places where they are sold
● Hospitals
● Chemist shops
Delhi (7 parliament constituency) ➔ Legislative 70 constituency ➔ 235 Wards
In my ward, I can estimate that there are roughly 20 chemist shops.
Therefore, No. of chemist shops = 235 X 20 = 4,700 shops.
Each shop at an average may sell 10 strips (100 tablets).
Therefore, tablets sold = 4,700 X 100 = 470,000 or 470k tablets.
Population of Delhi = 1.5 Crore
Let there be a bed for every one in 5000 persons = 15,000,000/5,000 = 3,000 beds.
Let there be 30 beds per hospital = 3,000/30 = 100 hospitals
If at an average, a hospital sells 100 strips (1,000 tablets), then tablets sold by hospital =
100 X 1,000 = 100k.
Total number of tablets sold = 470k+100k = ​570k ​tablets.
Note, parameters like a number of beds or 1,000 persons or so on are also general
parameters which can help us to determine the quality of health-care in the country.
74|The Guessing Game
If the question was a number of paracetamol tablets sold in India, then take that India has
approx 550 constitutions ➔ Approx 5,000 state counselling seats ➔ 35,000 municipal
wards ➔ 20 chemist shops/ward = 700k chemist shops.
Similarly, Delhi has a better medical facility than the national average. Hence we can take
10,000 persons/bed to estimate hospitals.
Further, notice that these variations are in the general present for developing nations.
Developed nation do not have these many disciplinary in the data.
If we, for example, had to estimate for the state of California, then
US population ➔ 50 states ➔ the average population per state = 7 million
But since California is an industrial state and near the coastline, it’s population will be
slightly higher than the average/mean value. So, begin by taking 8 million citizens.
Also, we can estimate that one bed/500 persons may be available in California or one
bed/1000 persons, as it’s medical facilities will be better than Delhi.
75|The Guessing Game
CASE 36
Estimate the no. of lakes in the world
Approach​:
​
Radius of the Earth=6400 km=2​6 X100
km
​
​
​
Therefore, the surface area of the Earth=4 X 3.14 X 2​6 X
2​6 X
100 X 100km​2 =
12.56
2
X 4,096 X 10,000km​
Assuming Earth to be a perfect sphere ~ 510 million km​2​.
Earth:● Water(70%) (357.5million km​2​)
● Land(30%) (152.5 million km​2​)
98% of the water on earth is in the ocean and sea. That is approximately 350 million
square kilometres.
The rest 2 %, i.e., 7 million square kilometres.
Out of the total freshwater 98% is in the form of glaciers(6.84 million square kilometres).
The rest 2% of the freshwater(0.16 million square kilometres) is in the form of rivers,
lakes and ponds.
Out of this 0.16 million square kilometres 85% in the form of rivers(119,000km​2​), 10% in
the form of lakes(14,000km​2​) and 5% in the form of ponds(7,000km​2​) .
76|The Guessing Game
Now let us take that an average size of a lake is 1,000mt X 100mt = 0.01km​2​.
Total no. of lakes = 14,000 X 100=​ 1​ 4 lakh lakes
(According to Google, we have approximately 20 lakh lakes. But these can be both
saltwater and freshwater lakes.)
Also, we can say that these lakes are natural lakes. There may be some artificial lakes
made by human beings for their use.
Lakes can be classified as:● Freshwater lakes
● Saline Lakes
Lakes can also be classified as:● Natural
● Man-made (or) Artificial
CASE 37
Estimating the size of the tyre industry in India in 2020
The population of India = 125 crores with the average family size of 4 to 5 = 30 crore to
25 crore
Say we take 27 crore families in India
Low income​ – No one will own an SUV
Mid/High income​ – These people may own a new/used SUV.
SUV by high end people​= 2.7 crore (0.5+0.6=0.3)
2.7crore*1.4=3.5 crores
Assuming that the average life of an SUV is 15 years, we have
sold
350/15 lac SUV
77|The Guessing Game
Approx. 2 million SUV = 20 lac SUV
So weave
26.6 lakhs new SUV sold in India in 202 and a total of 4.2 crore SUV in the country.
Also, let us assume that 12% of the new SUV sold in India (brought by Indian) are
explored abroad.
Therefore, the new SUV requires 5 tyres
=
150 lakh tyres for new SUVs.
(4tyre+1extra)
Let every one out of five cars require a tyre replacement in a year.
è 350/5*1=70 lakh replacement tyres.
Total tyres = 150lakh+70lakh
=
220lakh
( over 22 million tyre)
Revenue of the SUV tyre industry – Let the average price of the tyre be 10,000.
220 million * 10,000
= ​Rs. 220 billion
Revenue in = $ 220/60 billion = $ 3.67 billion
US $ term
78|The Guessing Game
CASE 38
Number of roses sold in Delhi on 14​th​ February
Delhi population = 1.5 crore
Now, everyone will not celebrate Valentine day by giving a rose.
Therefore, approximately 1.5 lac roses can be sold on 14​th​ February in Delhi.
180K Roses.
Follow up question -> Estimate the number of roses sold by a flower vendor in Delhi on
14​th​ February.
A-- 350 Vendors (shops)
But during the 14​th​ February, various street vendors do also sell roses.
79|The Guessing Game
They are primary at metro stations and markets.
The number of metro stations = 5 metro lines * 40 average number of stations per line.
B -- 200 stations
At an average 3 vendors per station (one vendor /entry or exit gate) = 600 vendors.
Again 70 constituencies, taking 2 markets per constituency approximately 150 markets.
5 vendors per market => C-- 750 vendors
Total vendors = 350+600+750
= 1800 Vendors
Average number of roses sold per vendor = 150000/1800 = ​83 rose
Average revenue =
average price * unit sold
(taking the average = 25*83
price to be 25
rupees per rose)
= 8300/4
=​ 2075 /vendor
80|The Guessing Game
CASE- 42.
Estimate the average distance run by a football player in an average match.
(45-90 metres and 90-120 metres)
A football match is of two halves, each of 45 minutes and the stoppage time is added to
each half.
So, the total playing time is 90 minutes and stoppage time compensates for any delays.
Generally, the attacker/defender disperses a distance of two-thirds of the whole field.
Now, average length of field = 2/3*105 m = 70m
dispersed by a player
The average width of field = 65mtrs
Generally, a player travels half the width = 35mtrs approx.
At an average, let the player move along this area and in round trip travels covers a
distance = 70+ 70+20+20 =180mtrs
Let a player do this in every 2 minutes (Time period between making the next goal
attempt).
81|The Guessing Game
And thus 45 attempts are made in the whole match.
Also, let the person remain on the field for 2/3​rd​ of the time and is substituted for the
remaining time.
Therefore, average distance covered = 180*45*2/3 = 5400mtrs = ​5.4kms​.
CASE -43.
Estimate the power consumed in your house in a day
Power consumed on a summer day will be different from that on a winter day. We will
show the summer day as from there winter day calculations can be visualized easily.
● The power rating of AC - 1 unit/hour
No. of ACs = 2
1. 1 AC operates for 3 hours (during daytime)
2. 2 ACs operate for 3 hours (during night time)
Therefore, 9 hours / day = 9 units / day.
● Power rating of a Refrigerator = 0.2 units / hour
1. No. of hours working in a day = 22 hours
Therefore, 4.4 units/day.
82|The Guessing Game
● Power Rating of a water pump = 2units/hour
Usage = 1 hour / day
Therefore, 2 units/day.
● Power Rating of a microwave oven= 0.5 units/hour
1. Usage = 1 hour
Therefore, 0.5 units / day.
● Power Rating of a water heater= 1units/hour
1. Usage = 2 hour / day
Therefore, 2 units/day.
● No. of fans in the home = 3 bedrooms + 3 washrooms + 1 kitchen + 2
Drawing rooms
= 5(ceiling fans) + 4(exhaust fans)
Power Rating of fans = 0.1 units / hour
Usage = 2 hours / day for exhaust fan+22 hours / day for ceiling fan
=(2*4 + 9*22)*0.1 units/day
= 19.8 + 0.8 units
=20.6 units/day
● No. of Lamps /Tubelight = 5 *3 bedrooms + 3*3 washrooms + 8*1 drawing
rooms + 481 kitchen
=36 lamps / tubelight
Average power rating = 0.025 units/day
Average usage= 10 hours/day for each lamp/tube light
=0.025*36*10
=9 units/day
● Power rating of a TV = 0.3 units/ day
Average usage = 3 hours / day
no. of TV = 2
Therefore, 1.8 units/day
● Power consumption of a laptop /PC = 0.4 units / day
Average usage= 2.5 hours / day
Therefore, 1 unit/day.
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Average Power consumption of electronic gadgets like mobile phone, electric iron, other
kitchen types of equipment like a grinder, juicer etc = 2 units/day
Therefore total consumption = 57.3 units / day
Monthly bill during summer = 57.3*30 = 1719 units / month
Average cost of electricity = Rs. 6 / unit
= 1719*6=​Rs. 10,314/month
Approx 10k /month
CASE- 44.
Estimate the number of youtube videos streamed in Delhi on a day
● The population of Delhi - 1.5 crores.
Delhi
Below Poverty Line
Above Poverty Line
(15%)
(85%)
20 Lakhs
1.3 Crores
(These people have mobile
access)
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Mobile Access
2G Handset
3G/4G Handset
(Feature phone)
(Smart Phone)
20%
80%
26 Lakhs
1.04 Crores
Internet Access Methods:
● Mobile Phone (80%)
● Broadband (20%)
● Cyber Cafe (~1%)
This means that out of a total of 1.5
crores people, 1.04 crores or
approx ⅔ rd have internet access.
Also, the amount of time spent will be different on a working day than a weekend.
Delhi Population
Below 20
Years
20-35 Years
35-50 Years
50-65 Years
65 Years and
above
33%
33%
16%
10%
8%
2 hrs/day
1.5 hrs/day
1 hr/day
Average time spent on the Internet
4 hrs/day
3 hrs/day
➔ 4 * ⅓ + 3 * ⅓ + 2 * ⅙ + 1.5 * 1/10 + 1 * 1/12
= 4/3 + 1 + ⅓ + 0.15 + 0.08 = 2.67 + 0.15 + 0.08 = 2.90 hrs/day
Time spent on the Internet - Internet Usage
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Social Network
Youtube
News or Music
Others
30%
20%
(approx 36 mins)
30%
20%
Y
​ outube Videos
Short duration below 6
mins
Medium Duration 6 - 20
mins
Long Duration 20 mins+
60 %
30%
10%
Songs, Trailers
Short Films, Shows, movie
clips
TV Series, Shows,
Educational Videos
Average Duration of Youtube Video
= 5 mins * 0.6 + 10 mins * 0.3 + 15 mins * 0.1 = 3 + 3 + 1.5 = 7.5 mins
​No. of youtube videos streamed
= 1 crore * 36 / 7.5 = 1 crore * 36/3 * 4/10 = 48/10 crore videos
● 4.8 crore​ times videos are streamed on youtube.
CASE 47.
Estimate the number of SRK fans in India.
​Population of India
● Male -65 crores
● Females - 60 crimes
The age-wise population of India
1. Below 20yrs - they will have a larger portion of new actors prefered.
2. 20-35 yrs
- this group will have a larger section of SRK fans.
3. 35-50 yrs
- this group will have a larger section of SRK fans.
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4. 50-65 yrs
- moderate SRK fans.
5. 65 and above - low %, as they prefer old actors.
Also, there are larger female fans than male fans.
Also, there will be a section who do not have any actor\actress as their favourite
Major actors
● Amitabh Bachan
● SRK
● Salman khan
● Actors like -Nawaj, Irfan, etc.
● New generation and others
Also, we assume that foreign actors are not considered.
Male fans
● Below 20 yrs - (33%) 10% SRK fans .
● 20-35 yrs - (33%) 16% SRK fans .
● 35-50 yrs - (16% ) 16% are SRk fans .
● 50-64 yrs - (10%) 12% are SRK fans .
● 65 yrs and above -(7%) 7% are SRK fans.
Total number of SRK fans (male) = 3.3% + 5,56% + 2.75% + 0.49%
=13.33% of total
=8.66 crore
Female fans
● Below 20 yrs -(33%) 12% are SRK fans .
● 20-35 yrs -(33%) 20% are SRK fans .
● 35-50 yrs - (16%) 20% are SRK fans .
● 50-65 yrs - (10%) 15% are SRK fans .
● 65 yrs and above - (7%) 10% are SRK fans.
Total number of SRK fans (female) = 19.36% of 60 crores.
= 11.61 crore.
The total number of SRK fans = ​20.27 crore​.
87|The Guessing Game
CASE 48.
Estimate the amount of money drawn from an ATM machine in Delhi in
one day.
Assuming the average time to withdraw money from an ATM machine is 90 seconds.
So in one hour, we can draw 60 / 1.5 = 40 withdrawals.
Amount of money drawn from an ATM:
● Average of ₹500: 55% withdrawals.
● Average of ₹2000: 30% withdrawals.
88|The Guessing Game
● Average of ₹5000: 10% withdrawals.
● Average of ₹10000: 5% withdrawals.
As generally, people withdraw money from an ATM when they are out of cash or when
they have to purchase something from a place where a card is not accepted. In Delhi
generally, we have swipe machines at outlets and have the former cause no more likely.
Average withdrawal amount per person= 0.55 x 500 + 0.3 x 2000 + 0.1 x 5000 +
0.5x10000
= 275 + 600 + 500 + 500
= ₹ 1875 per withdrawal
Occupancy of an ATM:
● 6-9 am: 40%
● 9am-12pm: 50%
● 12-4pm : 60%
● 4-7 pm: 70%
● 7-10pm: 60%
● 10pm-6 am: 10%
Average occupancy = [0.4 x 3 + 0.5 x 3 + 0.6 x 4 + 0.7 x 3 + 0.1 x 8 ] / 24
= (6.6 + 0.8) / 24
= 7.4 / 24 (approx 30% occupancy)
Total withdrawal = ₹1875 x 24 hours x 40 withdrawals/ hour x 30% occupancy
= ₹1875 x 24 x 40 x 0.3
=​₹ 5,40,000
Note:​ that the occupancy of the ATM depends upon its location. Occupancy will be higher
for an ATM located in a metro station near a hospital. It will be also higher at peak
market time (evening and afternoon time) if an ATM is located in a commercial
space/shopping market.
For an ATM located in a residential area, occupancy will be different. Similarly,
occupancy is also affected by other factors like the presence of other ATMs and bank
branches.
89|The Guessing Game
CASE 49.
Estimate the market size of formal ties in India on an annual basis.
Population- 125 crores or 1.25 billion.
People in working-age- 52.5 crores or 525 million
Division of 525 million people:
1.Agriculture and Fishery :50% (262.5 million)
2.Industry and Allied Sectors: 20%(105 million)
3.Services: 30%(157.5 million)
90|The Guessing Game
a.Organised Sector: 33% (52.5 million)
b.Unorganised Sector: 67%(105 million)
Note:​ Services include retail as well which has a large portion in the unorganised sector.
Distribution in the organised sector:
1. Dressing Code: Formal- 70%(36.75 million)
Many large scale companies, hotel chains, doctors and other service firms.
2. No Dressing Code: 30%(15.75 million)
Many startups, companies like Google.
Many people in the unorganised sector may also wear a tie, like many restaurants, small
retail outlets etc.
Unorganised sector: 105 million
1. Tie Required: 15%(15.75 million)
2. Tie not required: 85%(89.25 million)
Total number of people who use a tie as formal dressing = 36.75+15.75
=52.5 million
At an average let the ageing of the formal tie be as follows52.5 million:
1. No tie is purchased (20%)
2. Purchase 2 ties a year (20%)
3. Purchase 1 tie a year (50%)
4. Purchase 3 ties a year (10%)
Average tie purchased per person = 0.2x0+0.2x2+0.5x1+0.1x3
= 1.3 tie/person
No.of formal tie sold= 1.3x52.5 million =68.25 million
Now note that the question is to estimate the market size, this can be the revenue
generated or can be the number of ties sold.
Revenue generated by the formal tie industry=
= 68.25 million x cost of one tie
= 68.25 million x 100 INR
= 6825 million INR or 6.825
billion INR
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In dollar terms,
= 6825/65 million dollars
= ​105 million dollars annually​.
Also, note that formal ties are not just used by office going people. They are also used in
formal events like parties, anniversary, marriages etc.
They are also used in school/ college events like MUN Debates or other presentation
based competitions.
( The above two regions are not explored)
CASE 50.
Estimate the annual size of socks sales in India.
Population of India = 125 crores
Distribution of 125 crores:
1. Below poverty line: 20%
2. Low income: 40%
92|The Guessing Game
3. Middle income: 30%
4. High income: 10%
Population who can afford socks = 80% of 125 crore
= 100 crore
Age-wise usage:
1. Below 20 years: 33%
Generally, school and college-going age.
3 pair of socks for school and 3 for personal use.
2. Between 20 years to 65 years: 60%
A. Males: 50%
Employed: 90%
Unemployed: 10%
B. Females: 50%
Employed: 40%
Unemployed: 60%
3 pairs for office use and 3 for personal use annually.
3
​ ​. Above 65 years: 7%
3 pairs of socks annually.
Socks used by below 20 years population:
6 x ⅓ x 100 crore = 200 crores.
Socks used by population between 20 -65 years:
[6 x(0.3 x0.9 + 0.3 x0.4) + 3 x(0.3 x0.1 +0.3 x0.6)] x100 crore
= [6 x(0.39) + 3 x(0.21)] x100 crore
= (2.34 + 0.63) x100 crores
= 2.97 x100 crore
= 297 crores.
Socks used by population above 65 years of age:
7/100 x 100 crore x 3 = 21 crores.
Total socks sold = (200+297+21) crore
= 518 crores
Average cost of a sock = 50 INR/pair
Revenue = 50 INR x 518 crores
= 25900 crores or 259 billion INR
In dollar terms,
= $ 259/65 billion
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=​ $ 4 billion approx.
CASE 51.
Estimate the daily amount of water consumed by an Indian.
Water usage:
1. Drinking
2. Bathing and pooping
94|The Guessing Game
3.
4.
5.
6.
7.
Washing clothes, utensils, cars, scooters, bikes.
Cleaning of the house ( Dusting and mopping)
Watering plants
Hand wash, face wash etc.
Cooking food
Drinking( assuming summers )- 7 glasses of 200ml each - 1.4 L
Bathing(assuming summers)- 1 bucket of water - 40 L
- Pooping - 3 L
Washing clothes
We wash our clothes once in three days and we are a family of five.
Estimated water consumption:
= 15 buckets of water
= 15 x 40 L for 5 persons in 3 days
= 15 x 40 / 5 x 3 L per person/ day
= 40 L
Washing utensils- They are washed twice daily.
Estimated water consumption = 150 L
Therefore, per person per day consumption = 150/ 5 x 2 L = 15 L
Assuming that 1 bucket each is to clean two scooters and 1 bucket for a car.
2 buckets of water for a family of 5 = 2 x 40/ 5 L = 16 L/day
Cleaning of house = 1 bucket of water = 40/5 = 8L/day
Hand Wash = 3 times before having meal + 3 times after having meal
+ 5 times extra for various reasons
= 12 times handwash each consuming 200ml per wash
= 2.4L/day
Cooking food - 1.5L per meal for 5 person meal ( includes water used for cooking
vegetables and making flour)
= 1.5 x ⅗ L or 0.9L
Total water consumption = 1.4 +3 +40 +40 +16 +15 +8 +2.4 +0.9
= 123.7 L/day
Monthly consumption per person = 123.7 x 30
= 3711 L/monthly
Monthly consumption (family of five) = 3711 x 5 L/month
= ​18555 L/month​.
95|The Guessing Game
CASE 52.
Estimate the number of Indians on Twitter.
Distribution of Indians:
1. NRIs : 2.5% of the population = 2.5% of 1.25 crore = 31.25 million
a. Twitter: 60% ( approx 20 million)
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b. Non twitter presence: 40% (approx 11.25 million )
2. Non-NRIs: 125 crores
Many NRIs are present in Arab Nations and penetration of Facebook/ Twitter is
relatively low. Other major chunks are present in US/ Canada/ Europe which has good
twitter penetration.
Indian Residents: 125 crores
1. Internet Access: 70% ( 87.5 crores)
a. Urban: 40% (35 crores)
b. Rural: 60% (42.5 crores)
2. No Internet Access: 30% (37.5 crores)
Now Rural area has relatively low social media integration and urban people have higher
social media integration.
Social Media Integration:
1. Urban: 35 crore
a. Use social media: 80%(28 crore)
b. Don't use social media: 20%(7 crore)
2. Rural: 42.5 crore
a. Use social media: 20%(8.5 crore)
b. Don't use social media: 80%(34 crore)
Total population with social media presence = 28+8 crore
= 36 crore
Distribution of social media presence:
1. Facebook: Very high market share and impacts twitter market share (Market
Leader)
2. Youtube, WhatsApp, Others: Their market share doesn't impact Twitter's market
share
3. Twitter: very low market share ( 2nd position in terms of market share)
Age-wise usage of Twitter:
a. Below 20 years: 33% (7.5% use twitter)
b. Between 20 to 35 years: 33%(10% use twitter)
c. 35-50 years: 16%(5% use twitter)
d. 50-65 years: 10% 65 years and above: 7% (both combined use 2.5% of
twitter)
Average Penetration = (5%+6.33%+1.66%+0.85%) x ½
= 13.85% x ½
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= 24.93 crores
Similarly, if we had to estimate the number of Facebook users then the penetration would
have been much higher.
Age wise usage of Facebook:
1. Below 20 years: 33% (80% on Facebook)
2. 20-35 years: 33%(70% on Facebook)
3. 35-50 years: 16%(60% on Facebook)
4. 50-65 years: 10% 65 years above: 7% (both combined 25% on Facebook)
Average %age on Facebook = 0.8 x 33% + 0.7 x 33% +0.6 x 16% + 0.25 x 17%
= 64.25%
Number of Facebook users = 64.25% of 36 crore
= 23.13 crore
Or​ approx 231 million Facebook users.
Another follow up question can be to ​estimate the number of photographs of Indians on
Facebook.
Approx. number of users = 230 million
Facebook was launched in the year 2004 (February). Now it is the year 2019. 16 years
of life span.
Internet penetration in India has improved drastically in the last five years. So many users
have joined in the last five years only.
Therefore, the average time an Indian is on Facebook = 4 years approx.
Types of Facebook users:
1. Ones who add their photos at a fast pace (20%)
2. Ones who do not add their photos i.e, except on special occasions (60%)
3. Do not upload any photos (rarely use the Facebook or only browse it)(20%)
Let there be at an average of 10 instances (special occasion) on which photos are tagged.
Let there be at an average of 5 photos per tag.
Therefore, 80 photos a year for special occasions.
Let ones those add photos at a very fast pace add 5 photos a week
= 5 x 52 or 260 photos/year
Average number of photos added = 0.2 x 260 + 0.6 x 80
= 52+48
= 100 photos/year
Total photos added in 4 years = 4 x 100 = 400 photos
Total number of photos on Facebook of Indians = 400 x 230 million
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= 400 x 0.23 billion
=
​ 92 billion photographs
Note:​ Here photographs of Indian is considered. These do not include photos containing
memes or other stuff.
99|The Guessing Game